The present invention is directed to layer materials such as nonwoven webs, films, and the like, which are treated with acidic odor control compounds that are not easily washed away.
Nonwoven fabrics, films, foams, and other layer materials and their manufacture have been the subject of extensive development resulting in a wide variety of materials for numerous applications. For example, nonwovens of light basis weight and open structure are used in personal care items such as disposable diapers as liner fabrics that provide dry skin contact but readily transmit fluids to more absorbent materials which may also be nonwovens of a different composition and/or structure. Nonwovens of heavier weights may be designed with pore structures making them suitable for filtration, absorbent and barrier applications such as wrappers for items to be sterilized, wipers or protective garments for medical, veterinary or industrial uses. Even heavier weight nonwovens have been developed for recreational, agricultural and construction uses. Films, foams, and other layer materials are also employed in some of these applications, and may be combined with nonwoven webs.
For many thermoplastic layer material end use applications, it is desirable to reduce, prevent, or eliminate odors. For diapers and other incontinence products, it is desirable to reduce or eliminate the odor of ammonia which is present in urine. For feminine hygiene products, it is desirable to reduce or eliminate the odors of trimethylamine and triethylamine. Other common odor-producing substances include isovaleric acid, dimethyl disulfide, and dimethyl trisulfide.
Odor control agents include odor inhibitors, odor absorbers, odor adsorbers and other compounds which reduce, prevent, or eliminate odors. Odor inhibitors prevent the odor from forming. For example, U.S. Pat. No. 4,273,786 to Kraskin teaches the use of an aminopolycarboxylic acid compound for inhibiting the formation of ammonia from urea in urine. Odor absorbers and adsorbers remove odor after it is formed. Examples of odor control agents that remove odor by absorption or adsorption include activated carbon, silica, and cyclodextrin.
Acidic odor control agents based on carboxylic acids and their derivatives are used to neutralize or inhibit formation of odors from ammonia and other basic odor-forming compounds. Ammonia, released from aqueous ammonium hydroxide, is one of the primary odor-producing substances in urine. One of the drawbacks of acidic odor control agents is they are not inherently durable, i.e., they do not perform well after multiple insults with aqueous liquids. To the contrary, aqueous odor control agents are typically water-soluble, and can be easily washed away.
Water-insoluble, film-forming polymers can be used as a coating or binder applied to the layer material, to protect the acidic odor control agents from dissolution and washing. However, these polymers may also inhibit the performance of the odor control agents by preventing the ammonia from ever reaching them.
There is a need or desire for layer materials treated with acidic odor control agents which have durable odor control properties over multiple insults with an aqueous liquid. Specifically, there is a need or desire for a binder between carboxylic acid odor control agents and the layer materials which prevents or reduces the washing away of the odor control agents without significantly preventing or reducing their odor control performance.
The term xe2x80x9clayer materialxe2x80x9d refers to a material that exists in the form of a flexible, fabric-like or paper-like material, including without limitation nonwoven filament webs and fabrics, thermoplastic films, flexible thermoplastic foam materials, and multilayer combinations including one or more of these.
The term xe2x80x9cwater-permeable porous layer materialxe2x80x9d refers to a material present in one or more layers, such as a film, nonwoven fabric, or open-celled foam, which is porous, and which is water permeable due to the flow of water and other aqueous liquids through the pores. The pores in the film or foam, or spaces between fibers or filaments in a nonwoven web, are large enough and frequent enough to permit leakage and flow of liquid water through the material.
The term xe2x80x9cnonwoven fabric or webxe2x80x9d means a web having a structure of individual fibers or threads which are interlaid, but not in a regular or identifiable manner as in a knitted fabric. Nonwoven fabrics or webs have been formed from many processes such as, for example, meltblowing processes, spunbonding processes, air laying processes, and bonded carded web processes. The basis weight of nonwoven fabrics is usually expressed in ounces of material per square yard (osy) or grams per square meter (gsm) and the fiber diameters useful are usually expressed in microns. (Note that to convert from osy to gsm, multiply osy by 33.91.)
The term xe2x80x9cmicrofibersxe2x80x9d means small diameter fibers having an average diameter not greater than about 75 microns, for example, having an average diameter of from about 1 micron to about 50 microns, or more particularly, microfibers may have an average diameter of from about 1 micron to about 30 microns. Another frequently used expression of fiber size is denier, which is defined as grams per 9000 meters of a fiber. For a fiber having circular cross-section, denier may be calculated as fiber diameter in microns squared, multiplied by the density in grams/cc, multiplied by 0.00707. A lower denier indicates a finer fiber and a higher denier indicates a thicker or heavier fiber. For example, the diameter of a polypropylene fiber given as 15 microns may be converted to denier by squaring, multiplying the result by 0.89 g/cc and multiplying by 0.00707. Thus, a 15 micron polypropylene fiber has a denier of about 1.42 (152xc3x970.89xc3x970.00707=1.415). Outside the United States the unit of measurement is more commonly the xe2x80x9ctex,xe2x80x9d which is defined as the grams per kilometer of fiber. Tex may be calculated as denier/9.
The term xe2x80x9cspunbonded fibersxe2x80x9d refers to small diameter fibers which are formed by extruding molten thermoplastic material as filaments from a plurality of fine capillaries of a spinnerette having a circular or other configuration, with the diameter of the extruded filaments then being rapidly reduced as by, for example, in U.S. Pat. No. 4,340,563 to Appel et al., and U.S. Pat. No. 3,692,618 to Dorschner et al., U.S. Pat. No. 3,802,817 to Matsuki et al., U.S. Pat. Nos. 3,338,992 and 3,341,394 to Kinney, U.S. Pat. No. 3,502,763 to Hartmann, U.S. Pat. No. 3,502,538 to Petersen, and U.S. Pat. No. 3,542,615 to Dobo et al., each of which is incorporated herein in its entirety by reference. Spunbond fibers are quenched and generally not tacky when they are deposited onto a collecting surface. Spunbond fibers are generally continuous and often have average diameters larger than about 7 microns, more particularly, between about 10 and 30 microns.
The term xe2x80x9cmeltblown fibersxe2x80x9d means fibers formed by extruding a molten thermoplastic material through a plurality of fine, usually circular, die capillaries as molten threads or filaments into converging high velocity heated gas (e.g., air) streams which attenuate the filaments of molten thermoplastic material to reduce their diameter, which may be to microfiber diameter. Thereafter, the meltblown fibers are carried by the high velocity gas stream and are deposited on a collecting surface to form a web of randomly dispersed meltblown fibers. Such a process is disclosed for example, in U.S. Pat. No. 3,849,241 to Butin et al. Meltblown fibers are microfibers which may be continuous or discontinuous, are generally smaller than 10 microns in diameter, and are generally self bonding when deposited onto a collecting surface. Meltblown fibers used in the present invention are preferably substantially continuous in length.
The term xe2x80x9cfilmxe2x80x9d refers to a thermoplastic film made using a film extrusion process, such as a cast film or blown film extrusion process. The term xe2x80x9cwater-permeable porous filmsxe2x80x9d refers to films rendered porous by puncturing or aperturing, and to films rendered porous by mixing polymer with filler, forming a film from the mixture, and stretching the film.
The term xe2x80x9cfoam materialxe2x80x9d refers to a thermoplastic layer material made with the aid of a foaming process. The term xe2x80x9copen-celled foam materialxe2x80x9d refers to a foam layer whose cells interconnect, or otherwise create pores from one surface of the layer to the opposite surface.
The term xe2x80x9cpolymerxe2x80x9d includes, but is not limited to, homopolymers, copolymers, such as for example, block, graft, random and alternating copolymers, terpolymers, etc., and blends and modifications thereof. Furthermore, unless otherwise specifically limited, the term xe2x80x9cpolymerxe2x80x9d shall include all possible geometrical configurations of the material. These configurations include, but are not limited to isotactic, syndiotactic and atactic symmetries.
The term xe2x80x9ccarboxylic acid-based odor control agentxe2x80x9d includes odor control agents based on carboxylic acids and/or their partially neutralized salts. The term xe2x80x9cmulti-carboxylic acid-based odor control agentxe2x80x9d includes odor control agents based on dicarboxylic acids, tricarboxylic acids, polycarboxylic acids, polymeric polycarboxylic acids, etc., and/or their partially neutralized salts.
The term xe2x80x9cpolymeric polycarboxylic acidxe2x80x9d refers to a polymer having multiple carboxylic acid groups in its repeating units. Examples include polyacrylic acid polymers, polymaleic acid polymers, copolymers of acrylic acid, copolymers of maleic acid, and combinations thereof. Other examples are disclosed in U.S. Pat. No. 5,998,511, which is incorporated by reference.
The terms xe2x80x9csilicone polymer,xe2x80x9d xe2x80x9cpolyorganosiloxanexe2x80x9d and xe2x80x9cpolysiloxanexe2x80x9d interchangeably refer to siloxane polymers based on a structure of alternating silicon and oxygen atoms with various organic radicals attached to the silicon: 
The term xe2x80x9codor control systemxe2x80x9d refers collectively to individual odor control agents, and combinations (by chemical reaction and/or blending) of two or more odor control agents.
The present invention is directed to layer materials treated with a combination of odor control system and binder, where the odor control system includes a carboxylic acid odor control agent and the binder includes a polyorganosiloxane (i.e., silicone polymer). The inventors have found that silicone polymers serve as excellent binders between carboxylic odor control agents (and systems containing them) and thermoplastic layer materials, particularly layer materials based on polypropylene, polyethylene and other polyolefins. The silicone polymers have a unique ability to protect the acidic odor control agents from being dissolved or washed away by aqueous liquids, while at the same time permitting odoriferous gases such as ammonia to reach the odor control agents. Put another way, the silicone polymers are water insoluble, and at the same time are highly porous.
In one embodiment of the invention, the odor control system and silicone polymer are combined together, with the silicone polymer being in a molten form or dissolved or suspended in a solvent. The combination of odor control system and silicone polymer are applied to the layer material by spray coating, brushing, printing, dipping, extrusion, or the like.
In another embodiment of the invention, the odor control system is first applied to the layer material using spray coating, brushing, printing, dipping, extrusion, or the like. The silicone polymer is then applied to the layer material over the odor control agent using spray coating, brushing, printing, dipping, extrusion, or the like.
In one embodiment of the invention, the odor control system includes a multi-carboxylic acid-modified chitin or chitosan complex odor control agent. The carboxyl sites facilitate absorption of ammonia and amine-based odors. The amino groups on the chitin or chitosan facilitate absorption of acid-based odor compounds, and suppress the enzymatic decomposition of urine and menses, thereby inhibiting odor generation. This odor control complex can also be combined with activated carbon to provide additional control of amino, sulfuric and acidic odors.